It is often necessary to intravenously supply patients with pharmaceutically active liquids at a controlled rate over a period of time. Desirably, a patient remains in an ambulatory state while receiving the intravenous supply of pharmaceutically active liquids. Typical devices for accomplishing this purpose typically include an inflatable elastomeric bladder forming a liquid container and having a feature such as a flow control valve and tubing for supplying the liquid to the patient. The bladder has walls that are forced to expand when filled with the liquid and provide the pressure for expelling the liquid.
One drawback of conventional devices is that it is difficult for users, such as the patient or a caregiver, to discern whether the pump is providing the liquid, i.e., whether the device is dispensing liquid from the bladder. Accordingly, a device having an elastomeric pump and including features for indicating a change in volume of a bladder of the pump would be useful. Further, a device having an elastomeric pump that includes one or more features for communicating information about the operation of the pump based on an indicator for indicating a change in volume of a bladder of the pump would be beneficial. An indicator for indicating a change in volume of a bladder of an elastomeric pump that is easy to see and understand or interpret information indicated by the indicator would be desirable.